There has been a continuing and long-felt need for improving the oil/water ratio during hydrocarbon production by using chemical gel systems to resist the flow of injected or natural aqueous drive fluid through high permeability channels and fractures. This is sometimes referred to in the art as “conformance control.” The general approach has been to inject a mixture of reagents, initially low in viscosity, into a zone of the formation that has high permeability. After a sufficient time to allow the mixture to be pumped into the subterranean formation or when exposed to the elevated temperature of the formation, the mixture of reagents then forms a gel to block the flow of water. Several mixtures of reagents have been used in this way.
For example, U.S. Pat. No. 4,600,057 entitled “Method of Reducing the Permeability of a Subterranean Formation” issued Jul. 15, 1986, and having named inventor John K. Borchardt, discloses a method of reducing the permeability of a subterranean formation comprising contacting the formation with an aqueous polymerizable composition comprising a polymerization monomer, a polymerization catalyst having a latent period, and an alcoholic compound selected from the group consisting of a cyclic ether containing a hydroxymethylene substituent on a carbon atom bonded to the ether oxygen, an aliphatic alcohol having a carbon-to-carbon double bond or a carbon-to-carbon triple bond, and mixtures thereof. See Abstract. U.S. Pat. No. 4,600,057 is incorporated herein by reference in its entirety.
U.S. Pat. No. 4,640,361 entitled “Thermally Responsive Aqueous Silicate Mixtures and Use Thereof” issued Feb. 3, 1987, and having named inventors William H. Smith and Edward F. Vinson, discloses a thermally responsive aqueous silicate composition consisting essentially of an aqueous solution containing an alkali metal silicate and a thermally responsive silicate gelation activator. The thermally responsive silicate gelation activator is a reducing sugar selected from the group consisting of lactose, dextrose, fructose, galactose, mannose, maltose, xylose and mixtures thereof. The aqueous silicate composition can be utilized in treating a subterranean formation for the purpose of sealing the formation. See Abstract; U.S. Pat. No. 4,640,361 is incorporated herein by reference in its entirety.
U.S. Pat. No. 5,168,928 entitled “Preparation and Use of Gelable Silicate Solutions in Oil Field Applications” issued Dec. 8, 1992, and having named inventors Dralen T. Terry and Edward F. Vinson, discloses a gelable silicate solution prepared by mixing fumed silica and an alkali metal hydroxide with water. The silicate solution is used to form a seal or plug in one or more subterranean formations or in a well bore penetrating the formations by pumping the solution into a desired location in the well bore or formations and allowing the silicate solution to gel therein. See Abstract. U.S. Pat. No. 5,168,928 is incorporated herein by reference in its entirety.
U.S. Pat. No. 5,320,171 entitled “Method of Preventing Gas Coning and Fingering in a High Temperature Hydrocarbon Bearing Formation” issued Jun. 14, 1994, and having named inventor Mary A. H. Laramay, discloses a method of preventing gas coning or fingering from a gas cap in an oil producing well. A silicate solution and a delayed activator are injected into the gas cap under conditions such that the activator causes the silicate to gel after a predetermined period of time to form a substantially impermeable zone or layer above the oil bearing formation to prevent gas from flowing into the oil well during production. See Abstract. U.S. Pat. No. 5,320,171 is incorporated herein by reference in its entirety.
U.S. Pat. No. 5,335,726 entitled “Water Control” issued Aug. 9, 1994, and having named inventor Klein A. Rodrigues, discloses a method of forming a gel in a subsurface formation whereby a monomer is polymerized in the formation in the presence of a crosslinker by an initiator selected from azo compounds which are temperature activated over a range of temperatures. The method is particularly useful to substantially terminate or at least decrease the flow of water from a subterranean formation into a wellbore penetrating the formation. See Abstract. U.S. Pat. No. 5,335,726 is incorporated herein by reference in its entirety.
U.S. Pat. No. 5,358,051 entitled “Method of Water Control with Hydroxy Unsaturated Carbonyls” issued Oct. 25, 1994, and having named inventor Klein A. Rodrigues, discloses a method of forming a gel in the subsurface formation whereby a self crosslinking monomer selected from hydroxy unsaturated carbonyl compounds is polymerized in the formation by a suitable initiator. In a preferred embodiment, the initiator is selected from azo compounds which are temperature activated over a range of temperatures. The method is particularly useful to substantially terminate or at least decrease the flow of water from a subterranean formation into a wellbore penetrating the formation. See Abstract. U.S. Pat. No. 5,358,051 is incorporated herein by reference in its entirety. Without being limited by theory, it is now believed that the monomer is not self-crosslinking, rather, it is the difunctional monomeric by-product that causes the crosslinking,
U.S. Pat. No. 5,836,392 entitled “Oil And Gas Field Chemicals” issued Nov. 17, 1998, and having named inventor Phillip Lance Urlwin-Smith, discloses a method for conformance control of a reservoir comprising injecting into a zone of the reservoir an aqueous solution of a co-polymer comprising at least one ethylenically unsaturated polar monomer and at least one copolymerizable ethylenically unsaturated ester formed from a hydroxy compound of the formula ROH wherein R is a selected alkyl group, alkenyl group, cycloalkyl group, aryl group or such groups substituted with from 1 to 3 hydroxy, ether or thio ether groups or a heterocyclic or selected heterocyclic alkylene group and at least one heteroatom selected from oxygen, nitrogen and sulfur and a selected alkenoic or aralkenoic carboxylic acid or sulfonic or phosphoric acid together with a crosslinking agent comprising a multi-valent metal ion capable of crosslinking an acrylic acid polymer to form a viscous gel. The injected fluid is flowed through at least a portion of a high permeability region within said zone wherein it is heated to an elevated temperature whereupon crosslinking of the polymers occurs to form a substantially non-flowable gel within said high permeability region. The crosslinking of the injected fluid to form the non-flowable gel within the formation reduces the permeability of said region in said zone. See Abstract. U.S. Pat. No. 5,836,392 is incorporated herein by reference in its entirety.
U.S. Pat. No. 6,187,839 entitled “Methods of Sealing Compositions and Methods” issued Feb. 13, 2001, and having named inventors Larry Eoff and David Brown, provides methods of sealing subterranean zones using high density sealing compositions. The methods are basically comprised of introducing a sealing composition into the subterranean zone comprised of a high density aqueous salt solution, a polymerizable monomer and a polymerizable initiator and allowing said sealing composition to form a sealing gel in said zone. See Abstract. U.S. Pat. No. 6,187,839 is incorporated herein by reference in its entirety.
U.S. Pat. No. 6,192,986 entitled “Blocking Composition For Use In Subterranean Formation,” issued Feb. 27, 2001, and having named inventor Phillip Lance Urlwin-Smith, discloses a polymer composition for pumping downhole to gel in a subterranean formation comprising a water-soluble copolymer of (i) at least one non-acidic ethylenically unsaturated polar monomer and (ii) at least one copolymerisable ethylenically unsaturated ester; and an organic gelling agent therefor. See Abstract. U.S. Pat. No. 6,192,986 is incorporated herein by reference in its entirety.
U.S. patent application Ser. No. 10/826,615, entitled “Well Treatment Fluid and Methods for Blocking Permeability of a Subterranean Zone,” filed Apr. 16, 2004, by the assignee of the present invention, discloses a well treatment fluid for use in a well, the well treatment fluid comprising water, a water-soluble polymer comprising at least one unit of vinyl amine, and an organic compound that is crosslinked with the polymer. It also discloses a method of treating a subterranean formation penetrated by a wellbore, the method comprising the steps of: (a) forming a treatment fluid comprising water, a water-soluble polymer comprising at least one unit of vinyl amine, and an organic compound that is crosslinked with the polymer; and (b) introducing the treatment fluid through the wellbore and into contact with the formation. See Abstract. U.S. patent application Ser. No. 10/826,615 is herein incorporated by reference in its entirety.
The above compositions, however, often experience such a long delay in developing high viscosity that the composition are excessively diluted and displaced more deeply into the formation than desired. Consequently, the compositions may pass completely through highly permeable fractures, vugs and the like, instead of blocking them.